The Quinnipiac University survey, released Monday, also showed Lt. Gov. Michael Fedele gaining ground among likely voters in the Republican gubernatorial primary, but still trailing former ambassador Tom Foley.

The poll showed Lamont with 45 percent of the likely votes in his race, versus 42 percent for Malloy. The results fell within the margin of error of plus or minus 4.6 percentage points, poll director Douglas Schwartz said.

A poll released Aug. 5 had Lamont with a 45 percent to 40 percent lead over Malloy.

On the Republican side, Foley leads Fedele 38 percent to 30 percent, compared with 41 percent to 26 percent in the Aug. 5 poll. Hartford-area business advocate R. Nelson “Oz” Griebel had 17 percent of the likely vote in the latest poll, with 14 percent undecided.

The margin of error in the new GOP poll was plus or minus 3.8 percentage points.

Almost half the Republicans who named a candidate said they might change their mind before voting Tuesday.

The poll also shows wrestling company executive Linda McMahon with a 50 percent to 28 percent lead over former congressman Rob Simmons in the GOP primary for U.S. Senate, a seat held by Christopher Dodd for five terms. Weston money manager Peter Schiff received 15 percent of the likely voters’ support.

Schwartz said that while the Lamont-Foley race is a dead heat, the Foley-Fedele race also “could produce a surprise.”

“In the Republican Senate contest, it looks like Rob Simmons would need more than a surprise; he would need a miracle to catch Linda McMahon. But in politics, miracles do happen,” Schwartz said.

The winner of the Republican Senate primary will face Democratic Attorney General Richard Blumenthal in the general election.

The results come from polling 664 Connecticut Republicans and 464 Democrats who said they were likely to vote Tuesday, and who were picked from lists of people who have voted in past elections. The poll was conducted from Aug. 3 to 8.